An open-label study to evaluate the safety and effectiveness of GSK1605786A 500 mg twice daily over 108 weeks in adult subjects with Crohn's disease. Subjects completing previous GSK-sponsored studies with GSK1605786A or subjects who withdraw early from Study CCX114157 (maintenance study of GSK1605786A) due to worsening of Crohn's disease requiring a treatment change may be eligible to participate. The primary objective is to evaluate the safety of GSK1605786A, as assessed by recording of adverse events, clinical laboratory parameters, vital signs and electrocardiogram. Secondary objectives will include assessments of effectiveness of long-term treatment with GSK1605786A. Health outcomes assessments will include changes in Inflammatory Bowel Disease Questionnaire (IBDQ), SF-36v2, EQ-5D, Work and Productivity Activity Impairment-Crohn's Disease (WPAI-CD) and receipt of disability.